The present invention relates to storage batteries. More specifically, the present invention relates to protecting storage batteries from overdischarge.
Storage batteries, such as lead acid storage batteries of the type used in electrically propelled traction vehicles (such as forklift trucks and electric cars), have existed for many years. Such storage batteries consist of a plurality of individual storage cells electrically connected in series. By connecting the cells in series, the voltages of the individual cells are added in a cumulative manner to provide a total voltage that is sufficient to energize such vehicles.
In order to maintain long life and peak performance of such storage batteries, there are a few general preventative measures to be taken. One such measure is preventing the battery for being discharged below its working level. This not only protects the battery but also the major current carrying components of the vehicle in which the battery is employed.
Prevention of destructive deep discharging of the battery is typically carried out by a battery controller. Battery controllers are available in a variety of shapes, sizes and features. They are commonly referred to as battery discharge indicators, battery protection indicators, battery discharge alarms or simply battery gauges. All units provide some form of warning or visual indication to allow the vehicle operator to monitor battery charge status. In general, a low-charge warning or alarm is provided to the operator substantially immediately after the battery terminal voltage falls below a predetermined threshold. However, battery terminal voltage may be affected, for short periods of time, by parameters other than the battery's actual state of charge, such as by discharge current. Thus, low-charge warnings provided substantially immediately after the battery terminal voltage drops below the predetermined threshold may be inaccurate. A battery overdischarge protection scheme which addresses one or more of these or other problems not described would be an improvement in the art.